Second, Xie et al. showed a correlation of CDK5 and VEGF expression in pituitary adenomas [36], however, without proposing an underlying mechanism, and third, several studies exist, which show an influence of multi-kinase inhibitors on HIF-1α [37], or HIF-dependent gene expression [38], again, without mechanistic explanation. The gene discussed is HIF1A; the disease is pituitary gland adenoma.